Contact device for calling dials



July 22, 1947.

o. TSCHUM] 2,424,423

CONTACT DEVICE FOR mums DIALS Filed May 12, 1944 ,Hy.3. 5 .4. lmmwPatented July 22, 1947 2,424,423 CONTACT DEVICE FOR CALLING DIALS OttoTschiimi, Soleur e, Switzerland, assignor to AutophonAktiengesellschaft, Soleure, Switzerland, a joint-stock company ofSwitzerland Application May 12, 1944, Serial No.

In Switzerland May 21, 1943 2 Claims.

This invention relates to contact devices for calling dials.

Calling dials of known construction have, besides the impulse contact,an auxiliary contact short-circuiting the speaking set. This auxiliarycontact, on the advance movement of the call disc, was up to date closedby special means and remained sulted in the fact that after theoperation of the receiver contact one had to wait for the selectingsignal before the selecting operation could be commenced by advancingthe call disc, because the speaking set was short-circuited by theabove-mentioned auxiliary contact immediately after the beginning of theadvance movement of the call disc.

Another disadvantage of this known arrangement resides in the fact that,during the operation of the call disc, i. e. during the shortcircuitinof the speaking set, even the busy tone could not be heard by thecalling subscriber. This busy tone was only audible in the short periodsof rest position of the call disc, so that, on a quick selecting of thedifferent figures, this tone was not caught by the calling person andcould thus only be heard when the selection was already accomplished.This resulted in too long a seizure of the main station and in the riskof making faulty switching operations.

The contact device according to the invention is characterised in thatit comprises a contact which, on the advance movement of the call disc,short-circuits the speaking set for, at most, a short time.

According to the invention, the contact is not closed before the returnmovement of the call disc begins. In this way not only the requirementsmade with regard to the subscribers selecmaterial whether theestablishment of connection is commenced by the operation of thereceiver contact or of the call disc. A busy tone can be heard in therest position or during the advance movement of the call disc. Besidesthis, the subscriber can bring the call disc at once into the advancedposition so that, on receiving the selecting sign, he can immediatelygive out the impulses by letting the call disc go, the time of seizurebeing thereby considerably reduced and the establishment of theconnection accelerated.

The accompanying drawing illustrates, by way of examples, difierentembodiments of the object of invention.

Fig. 1 is a diagrammatic view of a first, and

Fig. 2 is similar view of a second embodiment,

Figs. 3 and 4 show a mechanical part of a third example in differentviews.

Fig. 1 represents an application in remote-controlled devices. Thespeaking set G is connected to the subscribers line a-b which can beshortcircuited by the R, the impulse contact 2' and the relay contact11, bridged-over by the condenser C, are connected in series to thespeaking set G. Contact is is ara way that it is closed during theadvance movement of the call disc for a short time. and during the wholereturn movement of the disc.

The manner of operation is as follows:

In the case of remote control an alternating current impulse, forinstance, is given to the device (over the condenser C an alternatingcurrent lishment can be commenced.

If the connection is, to be established by the subscriber himself, hedials his call disc in accordcall disc for other purposes than for thesubscribers self-connection only.

Fig. 2 shows another example of application of I the contact operationaccording to the invention in a remote-controlled subscribers station,in which the call disc carries out the additional operation of changingthe speaking direction.

The subscribers amplifier and electro-acoustic transformer are connectedto the terminals A while the opposite side of the repeater U leads tothe transmission conductor a-b which can be short-circuited by thecontact k. The middle of the transmission winding lying on the side ofthe network is earthed over relay R, contact 11 and the impulse contacti. Contact n is bridged-over, both by the condenser C and the contact761.

The remote control and the control by the subscriber himself areanalogous to thatof' the example in Fig. 1, however, with the difierencethat contact is only short-circuits the speaking set during the returnof the calling disc, whilecontact k1, owing to its short-time actionduringthe ad:

vance movement of the calling disc, causes the closing of the directcurrent path and thereby the subscribers self-connection. Thetransmission of the impulses to the earth takes place by means of theimpulse contact 2', while the speaking and selecting signals go over theline a-b and the repeater U to the terminals A. The short-circuiting ofthe line a-b is, in the first place, not effected with regard to theselecting impulses which inthe case of complete symmetry are, at allevents, not audible, but with regard to the surges which, during theswitching-over operations, would be transmitted to the line.

The contact operation according to the .invention which, in thisexample, is characterised in that the contact is short-circuiting theline ab is not closed during the whole operation of the call disc butonly during the return movement of the latter, presents the additionaladvantage that the time necessary for changing over the speakingdirection (by a corresponding operation of the call disc) isconsiderably reduced.

Figs. 3 and 4 illustrate the mechanical part of another example in whichthe contact is is closed during the return movement of the call discuntil the latter is at rest.

The rotation of the call disc NS is transmitted to the cam n which, inrest position, is in contact with the insulated support s. This latterseparates the springs of the contact In as well as those of the contactk. Between the outer springs of the contact 70 an insulated pin 22 isinserted which can be operated by the spring J. The nose 6 of thisspring I is in contact with the driver m rigidly fixed to the undersideof the impulse disc is taking along the driver.

The manner of action is as follows:

Q comesii'nto contact with the driver m If the call disc is advanced inthe direction of the arrow indicated in Fig. 4, the ridge of the cam 11,leaves the position shown and the insulated support S is released,thereby allowing the contact R1 to be closed. Contact is would also beclosed if the insulated pin 1) should not keep the springs of thiscontact in separated position. It may thus be seen that during theadvance movement of the call disc the contact k1 is closed, whilecontact 10 remains open. When the return movement of the call discbegins, the impulse disc is with the driver m is put into rotation in aknown manner. Thereby the nose e of the spring I in such a way that theinsulated pin 1) is removed from its position between the outermostsprings of contact I; so that these springs can close the contact. Whenthe cam n arrives at the rest position, its ridge comes again intocontact with the support 3 and presses the latter to the right, wherebyboth contacts is and 701 are opened.

By these simple mechanical means it is possible to obtain the operationof the contact 7c according to the invention.

What I claim is:

1. In a contact device for calling dials of a speaking unit, two springsforming a contact for shortcircuiting the speaking unit, a pin betweensaid springs adjusted to keep said contact open, and a means foractuating the said pin to close the contact at most a short time duringthe advance movement and during the whole return movement of the callingdial.

2. In a contact device for calling dials of a speaking unit, two springsforming a contact for shortcircuiting the speaking unit, a pin betweensaid springs adjusted to keep the said contact open, a member connectedwith said pin to withdraw the latter from the space between saidsprings, an impulse disc, a driver connected with said impulse disc andadjusted to cooperate with said member to withdraw said pin during thewhole return movement of the calling dial.

OTTO TsciriiMI.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,652,645 Shull Dec. 13, 192"!1,551,626 Smith Sept. 1, 1925 1,424,368 Martin Aug. 1, 1922

